1. Field of the Invention
The present invention relates to a heat pump type hot water supply outdoor apparatus having a water heat exchanger and an injection circuit.
2. Description of the Related Art
It is disclosed that since conventional air conditioners have an injection circuit and a circulation amount of refrigerant can be increased on an indoor heat exchanger side during a heating operation, they can secure a heating capability even at the time when an air conditioning load is large such as when an outside air temperature is low and the like. However, nothing is disclosed as to an advantage and a control method in a case when it is applied to a heat pump hot water supply outdoor apparatus having a water heat exchanger (refer to, for example, Japanese Unexamined Patent Application Publication No. 2006-258343 (FIG. 1 of page 1)).
The conventional air conditioner having the injection circuit determines whether or not an injection control is carried out based on an outside air temperature during a heating operation.
The injection control is carried out to exhibit an advantage of obtaining a high heating capability at the time when the ratio (compression ratio) between the pressure (high pressure) of the refrigerant discharged from a compressor and the pressure (low pressure) of the refrigerant sucked into the compressor.
Accordingly, when an outside air temperature is reduced at the time when the air conditioner carries out the heating operation, the compression ratio is increased because an evaporation temperature is reduced and a suction pressure is also reduced.
Thus, the injection control is carried out when the outside air temperature is reduced. This is because since a condensing temperature corresponding to high pressure changes only in the range of from about 35° C. to 50° C. in a case where it is used for the air conditioner, a state in which the compression ratio is high can be assumed by an outside air temperature by which a low pressure is determined.
However, in a heat pump type hot water supply outdoor apparatus, a condensing temperature corresponding to the high pressure changes within the wide range of from 20° C. to 65° C. or more. As a result, when whether or not the injection control is carried out is determined only by the outside air temperature, a problem arises in that a capability becomes insufficient because the injection control is not carried out regardless of a condition that the compression ratio is high or the capability is excessively increased because the injection control is carried out in a condition that the compression ratio is low.
Further, when the injection control is carried out in the condition that the compression ratio is low, since the discharge temperature of a compressor is reduced, the reliability of the compressor may be deteriorated.
Accordingly, the heat pump type hot water supply outdoor apparatus has a problem in that an optimum injection control cannot be realized only by the outside air temperature.
An object of the present invention, which was made to solve the above problems, is to obtain a heat pump type hot water supply outdoor apparatus which can realize an appropriate injection control, can permit a long period of time of use of equipment because the reliability thereof can be secured even if an outside air temperature and the temperature of supplied hot water change, can carry out a high hot water supply/heating capability operation or a highly effective hot water supply/heating operation, and can reduce energy consumption.